# -*- coding: utf-8 -*-
"""
Created on Mon May 20 17:28:35 2019

@author: yaoyu
"""

import numpy as np
import matplotlib.pyplot as plt
x = np.arange(1,13,1)*3
y = range(1,13,1)
plt.plot(x,y)
xx = range(0,13,4)
plt.xticks(xx)
plt.show()